1. In most cases spam is posted by botsw.
2. Spammers now hire people to post bogus comments.
3. IP blocking has gone the way of the dodo bird.
These people can get a new IP in the blink of an eye. So can you and so can I. ISP providers are saving $ by putting hundreds of us in the same IP block so if we get into “blocking” then we are blocking hundreds of innocents.
Advice: Moderate all comments. Mark “spam” that gets through Akismet unrecognized as spam. Skim through your spam filter every day and don’t get fixated on getting anyone because you can’t.